Bioretention cells are a stormwater treatment technology that uses soil and vegetation to remove pollutants from runoff and improve downstream water quality. While bioretention has been shown to be effective at removing certain stormwater pollutants such as sediment and heavy metals, removal of nutrients has been more variable. Design components of bioretention such as vegetation and soil media amendments can influence pollutant removal performance. In my experiment, I isolate the effects of low-phosphorus compost and a Switchgrass (Panicum virgatum) monoculture on bioretention performance. In fall 2016, three bioretention cells were installed at the University of Vermont Miller Research Complex, a mixed-use research and agricultural production facility located in South Burlington, VT. Each bioretention had a unique experimental treatment that allowed for the comparison of the presence of the following design components: (1) compost with planted vegetation, (2) no compost and vegetation, and (3) no compost or vegetation. Results suggest that the presence of a low-P compost layer had a small deleterious effect on nutrient removal performance, as the bioretention cell with an added compost layer exported higher concentrations of phosphorus and nitrogen and exhibited a higher concentration of water extractable phosphorus in the bioretention media. The bioretention cell with vegetation and no compost was the only treatment to significantly reduce total nitrogen and phosphorus concentrations; however, there was no effect on media phosphorus concentration. The presence of low-P compost significantly increased the above-ground biomass growth of Switchgrass, but had no effect on the total number of plants surviving in the first year. Switchgrass proved to be a durable plant, capable of surviving in bioretention media without compost, but was slow to grow and required additional watering through droughty conditions.

Eutrophication is defined as the ‘over enrichment’ of a water body from nutrients, resulting in uncontrolled growth of primary producers, leading to periods of oxygen depletion from decomposition of the algal organic matter. According to the 2010 Water Infrastructure Needs and Investment (a U.S. Congressional Report), 40% of U.S. water bodies are contaminated with pollutants, including nutrients. Non-point sources of nutrient pollution are a major cause of this reduction in water quality. One way to decrease eutrophication is to manage nutrients found in stormwater runoff, before they reach a receiving water body. Bioretention cells containing an internal water storage zone (IWSZ) have been shown to remove higher amounts of nitrogen than conventional cells (without an IWSZ). The IWSZ contains an organic carbon substrate, usually derived from wood chips submerged in water, which supports the biochemical process of denitrification. Characteristics of wood chips that affect nitrogen removal include carbon content (%), leaching of dissolved organic carbon (DOC), and wood chip size and type. However, there is limited information on how the intermittent hydraulic loading that is associated with these field systems impacts their performance. Accordingly, the overall goal of this research is to improve understanding of the effect that the antecedent dry conditions (ADC) have on the performance of a field scale bioretention cell modified to contain an IWSZ. The nine different types of wood chips used in laboratory and field studies identified in the literature were categorized as hardwood and softwood. Literature showed that total organic carbon (TOC) leached from softwood chips is almost double the TOC measured from the hardwood chips, 138.3 and 70.3 mg/L, respectively. The average observed nitrogen removal for softwood chips was found to be greater than the removal for the average of the hardwood chips (75.2% and 63.0%, respectively). Literature also suggests that larger wood chip size may limit the availability of the carbon for the denitrifying organisms and provides less surface area for the biofilm growth. A field study conducted for this research compared the performance of a modified bioretention system designed to enhance denitrification, addition of an IWSZ, with a conventional system that does not contain an IWSZ. Fourteen storm events were completed from January 2016 to July 2016 by replicating storm events previously completed in the laboratory using hydraulic loading rates (HLR) of 6.9 cm/h, 13.9 cm/h, and 4.1 cm/h. The goal was to have results from storm events with ADCs of two, four, and eight days, with the varying durations of hydraulic loading of two, four, and six hours. Synthetic stormwater, simulating nitrogen levels common in urban runoff, was used as the system’s influent to assist in running a controlled experiment. The resultant ADCs ranged from 0 to 33 days, with the average ADC being 9 days. The fourteen sets of influent samples were averaged to obtain mean influent concentrations for the synthetic stormwater. These values were used when calculating the percent nitrogen removal for the four measured nitrogen species (NOx – N, NH4+– N, organic N, and TN). The field storm events were separated into three groups based on HLR and duration to eliminate the affects of both variables on nitrogen removal for these results, since the focus is the ADC. For the low HLR (4.1 cm/hr), there were four storm events (ADCs of 4 to 33 days), as the ADC increased, greater percentages of ammonium – nitrogen, organic nitrogen, and total nitrogen were removed. For nitrate/nitrite – nitrogen, the percent removal was rather consistent for all four storm events, not significantly increasing or decreasing with changes in the ADC. There were five storm events (ADCs of 0 to 28 days) tested with the median HLR (6.9 cm/hr), nitrogen removal for all four species increased as the ADC increased. The increase was significant (p0.05) for nitrate/nitrite – nitrogen. The third group also contained five storm events (ADCs from 0 to 11 days) that were tested with the highest HLR (13.9 cm/hr). Ammonium – nitrogen, nitrate/nitrite – nitrogen, and total nitrogen all increased with the ADC, and organic nitrogen removal decreased with the increasing ADC. As a result, this research concluded that the difference in HLR affects the nitrogen removal efficiency, but overall increasing the ADC increased nitrogen removal for NOx – N, NH4+ - N, organic N, and TN.

Stormwater ponds (SWPs) are becoming increasingly important due to the negative impacts on flood mitigation and water quality control that results from rapid urbanization. These ponds are not only designed to control the discharge of large precipitation and snow melt events, but also to mitigate the water quality of the retained stormwater. Consequently, improper design and maintenance may lead to hypoxic conditions in SWPs, which result in poor water quality and generation of noxious gases. Riverside South Stormwater Pond II (RSPII) in Ottawa periodically experiences low dissolved oxygen (DO) concentrations and subsequently hypoxic conditions at depth in the pond, especially during summer days with less precipitation and winter ice covered periods. Hydrogen sulfide gas (H2S) has been generated and released into the ambient atmosphere during these periods of lesser water quality. Hence, there is a need to understand how DO spatial distribution and seasonal change trigger and affect H2S production. The conventional shallow design criteria of SWPs likely cause these systems to be susceptible to wind conditions. Very few research has demonstrated the correlation between wind-driven hydraulic performance and detained stormwater quality. Hence an understanding of pond-scale mixing generated by wind-induced flow and the subsequent correlation to DO concentrations and stratification in SWPs are important to understanding the water quality and performance of these systems, especially in a wind-induced flow dominated SWPs. The overall research objective is to develop a comprehensive understanding of hypoxic conditions of SWPs and to investigate the impact of wind induced hydraulics on DO seasonal characteristics and the subsequent production of H2S. RSPII was shown to experience lower DO and longer hypoxic conditions than an adjacent reference pond (RSPI) at both non-ice covered and ice covered months. In addition, hypoxia was shown to be initiated at the outlet of RSPII where the depth of the pond was a maximum. Interestingly, chlorophyll-α blooms were observed during ice covered conditions in the study, with synurids, tabellaria, and asterionella being identified as the dominant species. A bottom-mount acoustic Doppler current profiler (aDcp) was used to collect small wind-generated currents in RSPII. The three-dimensional current and DO model produced by MIKE 3 (DHI software) suggests a conclusive result of pond scale mixing produced by wind-driven flow as well as countercurrents near the bed opposite to wind direction. A wind dominated circulation was shown to be generated even with moderate wind speed, and with a higher wind condition pond-scale complete DO mixing was created. The MIKE 3 simulation further provided a comprehensive understanding of the correlation between wind-induced hydraulics and DO concentrations distribution in a shallow stormwater pond. Therefore, this research demonstrates that wind is an essential hydraulic driver in shallow ponds, which also likely affects water quality by initiating pond mixing.

It is no longer a question of scientific debate that research declares our climate is changing. One of the most important and visible impacts of this phenomenon is sea level rise which has impacts on coastal cities and island communities. Sea level rise also magnifies storm surges which can have severely damaging impacts on different human made infrastructure facilities near the shorelines in coastal zones. In this research we are concerned about the proximity of water systems as one of the most vulnerable infrastructures in the coastal zones because of the impact of stormwater combining with sewage water. In Canada, the government has plans to address these issues, but to date, there needs to be further attention to stormwater management in coastal zones across the country. This research discusses the impacts of severe environmental events, e.g., hurricanes and storm surge, on the water systems of selected coastal communities in Canada. The purpose of this research is to model coastal zone water systems using the open source StormWater Management Modelling (SWMM) software in order to manage stormwater and system response to storms and storm surge on water treatment plants in these areas. Arichat on Isle Madame, Cape Breton, one of the most sensitive coastal zones in Canada, is the focal point case study for this research as part of the C-Change International Community-University Research Alliance (ICURA) 2009-2015 project.

Weekly collections were conducted from May to December, 2007 (153 trap nights, total) in Denton, Texas, in and around large storm drains and overpass drainage facilities in residential and non-residential areas, using Centers for Disease Control (CDC) light traps and gravid traps. A total of 1964 mosquitoes were collected, representing 24 species within 6 genera: Aedes, Anopheles, Culiseta, Culex, Psorophora, and Uranotaenia. Culex was the most abundant genus, representing 75% of all mosquitoes collected; Aedes was the second most abundant, representing 12 % of all mosquitoes collected. Cx. quinquefasciatus was the dominant species collected via gravid traps; Cx. (Melanoconion) species were the dominant species collected via CDC light traps. Data of gravid traps and light traps were analyzed separately using nonparametric correlation analysis, comparing environmental data and physical characteristics to total abundance of mosquitoes. There was no significant correlation found when comparing the three dominant species collected in light traps (unidentified Cx. (Melanoconion) sp, Cx. quinquefasciatus, and Ae. vexans) to environmental characteristics and physical characteristics. Analysis of Cx. quinquefasciatus collected in gravid traps indicated no significant correlation between abundance, environmental data, and physical characteristics. Linear regression models were analyzed to determine if either environmental variables or physical characteristics of the drainage system explained the species abundance collected; no individual variable showed an association of significance. Analysis of Cx. quinquefasciatus collected in storm drains via gravid traps determined temperature to be the most important variable in determining population abundance and explained 99% of the population variability.

Bioretention cells have become a commonly used green infrastructure technique to help infiltrate and remove contaminants from stormwater runoff. Bioretention cells are constructed from a layered or heterogeneous soil mixture designed to optimize their ability to infiltrate influent stormwater and remove contaminants carried by the water as it filters through the soil media. The soil mixture, composition, and planting vary depending the local regulatory agencies. As urbanization occurs across the United States, more natural land is converted from pervious surfaces, such as grasslands and forests, to impervious surfaces such as asphalt and concrete, to help reduce the impact of the runoff generated by this increased flow bioretention cells are an often-used method to treat stormwater. These impervious surfaces do not allow rainfall to infiltrate, and the water runs off into receiving water bodies such as rivers and streams as a non-point source pollutant. To help reduce pollutant loadings into receiving water bodies, Low Impact Development (LID) techniques were developed to reduce stormwater volume, peak flow, and contaminant loading rates. The bioretention cell is one of the most popular LID techniques and is comprised of a soil media that is either a layered or homogenous media, which is built following a regional agency’s standard. The performance of bioretention soil media is highly variable depending on the amount of each soil constituent present in the media. This study compares five different soil mixtures from various agencies’ specifications to determine which media composition is most effective at removing total suspended solids (TSS) and nitrates, two of the most prevalent contaminates carried by stormwater. This study also compares mixtures’ hydraulic conductivity which determines the volume of water that the media can infiltrate and “treat”. To perform these tests, six columns of soil media were constructed with media depths of 91.5 cm (36 inches). Columns were dosed with either tap water (Phase I) or a synthetic stormwater blend (Phase II) to determine the amount of TSS and nitrate exported by each mixture. The soil mixture in each column was characterized to understand how soil characteristics effect the performance of the various media mixtures. The bioretention soil media columns were all shown to be effective at removing influent TSS with an average removal rate of over 88% across all the columns, ranging from 99.9% removal to 73.6% removal. Most bioretention soil mixtures used in the test were shown to be ineffective at removing influent nitrates, with breakthrough of nitrate occurring after the first two pore volumes. Interestingly, the media with higher organic content were more effective at removing nitrates, with removal rates as high as 59.9% compared to the media with lower organic content. Hydraulic conductivity was also highly variable across the various soil media mixtures depending on the percentage of sand and fine media particles present in the media. Hydraulic conductivity ranged from a high value of 42 cm/hr to a low of 8.3 cm/hr. By comparing these results, a more effective bioretention soil media mixture can become agency standard and allow bioretention cells to have more consistent and better performance.

Integrating green or blue space into cities can provide environmental and public health benefits which maximize urban sustainability. One type of green/blue infrastructure that has been understudied is urban stormwater ponds, which are used to manage stormwater runoff. Their performance is typically only evaluated in terms of hydrological functions, with little focus on their capacity to provide ancillary benefits to communities. In this exploratory study, an online survey was distributed to six neighbourhoods in the City of Ottawa, ON to gain insight into the social value of urban stormwater ponds. The results revealed that despite some disadvantages, most respondents visited their neighbourhood stormwater ponds regularly and largely appreciated the cultural ecosystem services provided by these ponds, such as opportunities for experiencing nature, especially wildlife, and outdoor recreation. These findings can be used to improve the multifunctionality of stormwater ponds and optimize both environmental and social sustainability outcomes.

An important source of freshwater in arid lands is found in groundwater aquifers that are recharged after storm events. However, most of the precipitation is lost due to evaporation and only small fractions actually recharge the aquifers. The construction of dams along wadi channels enables the retention of stormwater, however the reservoirs are still subject to huge evaporative losses and contamination. In this study, the hydraulic properties of a dunefield in western Saudi Arabia are evaluated in order to determine the feasibility of designing a stormwater storage aquifer storage and recovery facility using the dune sands as a natural medium and design recommendations are addressed. The accurate estimation of hydraulic conductivity of unlithified sediments such as dune sands has become very important in the design of natural filtration projects, including aquifer recharge and recovery systems. Therefore, a comparison and selection of methods for the determination of the hydraulic conductivity from grain size distribution found in the literature was done. An improvement to these equations based on measurements on dune samples was obtained.

The goal of this study is to develop a model using GIS to estimate the source and quantity of accumulated sediment in the Emory & Henry College (EHC) duck pond.  Located in the Highlands of Southwest Virginia, the 1,194 acre duck pond watershed consists primarily of agricultural, forested, and low density urban land uses. The Revised Universal Soil Loss Equation (RUSLE) and the Sediment Distributed Delivery (SEDD) prediction models were used to determine the quantity of eroded sediment and the sediment yield at the duck pond, respectively.  These models require numerous computations, which were performed at the watershed scale with the aid of ArcGIS software.  In ArcGIS the watershed was broken into a raster grid of approximately 5,200 discrete 100 foot by 100 foot grid cells. The resulting watershed erosion model identified two main sources of sediment: a cluster of farms relatively close to and east of the duck pond, and a harvested timber site north of the duck pond.  The model predicted that 1,076 tons of sediment are delivered into the duck pond annually. The estimated sediment yield was then compared to the estimated amount deposited between October 2011 and September 2012, as measured by a topographic survey.  The model prediction was found to be within a factor of 6.3x of the measured value.  The predicted and measured sediment yields as well as identified erosion sources can be used to develop a water quality improvement plan and to help alleviate the need for periodic dredging. / Master of Science

In recent years, green roofs have become an accepted solution in ecological urban design to mitigate the impacts of impervious surfaces (Berghage, Beattie, Jarrett, Thuring, & Razaei, 2009). An experimental research project was conducted at the Mississippi Agriculture and Forestry Experiment Station (MAFES) Green Infrastructure Research Area at South Farm of Mississippi State University to determine how medium depth and slope gradient on rooftops affect plant cover and survival. Plant cover was monitored monthly by photographing the experimental green roof platforms. Photoshop and AutoCAD software programs were employed to digitize and to calculate plant cover from the images. All recorded data was analyzed with Analysis of Variance (ANOVA) tests. It was determined that the effects of medium depth and slope are statistically significant on plant cover and survival.